KR102458084B1 - Emulsified acid composition for carbonate acidizing and method for preparation - Google Patents

Abstract

The present invention relates to an emulsified acid composition for carbonate rock reservoir acidizing, and more specifically, to: an emulsified acid composition for carbonate rock reservoir acidizing with new composition, which has an effective acid-rock reaction delay effect and acid treatment efficiency in low permeability or heterogeneous carbonate rocks, through fluid stability that phase separation does not occur at room temperature and high temperatures; a preparation method thereof; and a rock acid treatment method for carbonate rock reservoirs using the same. The emulsified acid composition includes 65-75 vol% of a hydrochloric acid aqueous solution and 25-35 vol% of a mixed emulsifier diesel solution.

Description

Emulsified acid composition for carbonate acidizing and method for preparation

The present invention relates to an emulsified acid composition for acid treatment of carbonate rock storage, and more specifically, effective acid-rock reaction delay effect in carbonate rocks with low permeability or heterogeneity through fluid stability in which phase separation does not occur at room temperature and high temperature, and The present invention relates to an emulsified acid composition for acid treatment of a carbonate rock reservoir having a novel composition having acid treatment efficiency, a method for manufacturing the same, and a method for treating a rock body of a carbonate rock reservoir using the same.

Despite entering the era of energy transition, the role of traditional petroleum resources is expected to be strengthened, and the importance of securing resources is emphasized. In particular, even if the demand for oil for automobiles decreases due to the spread of electric vehicles and the development of battery technology, the demand for non-substitutable oil in other transportation parts such as ships and aircraft is expected to maintain a steady increase in the long term (Korea Energy Economics Institute, 2020). In order to meet the increasing demand for oil, petroleum resource development must be continued, and interest in carbonate rock reservoirs, which is known to contain more than 60% of the world's oil, is increasing (Schlumberger, 2020). However, carbonate rock reservoirs have a problem in that the primary recovery rate is significantly lower than that of sandstone reservoirs, which are easy to develop and produce due to large heterogeneity and complicated flow characteristics. Therefore, in petroleum development sites, matrix acidizing is generally performed to improve productivity by improving the permeability of carbonate rock reservoirs (Sayed et al., 2013; Yousufi et al., 2018; Yoo and Lee, 2018; Yoo et al., 2018; Yoo et al., 2019). At this time, hydrochloric acid (HCl) is mainly used for acid treatment of rocks because it has excellent reactivity with carbonate rocks made of calcite and dolomite and is also inexpensive. However, hydrochloric acid has a problem in that it flows only to the stratum with high permeability when injected into a heterogeneous reservoir due to its low viscosity, so there is a disadvantage in that the permeability improvement occurs partially. In addition, at a low injection rate, a large amount of corrosion inhibitor is used to prevent face dissolution, in which only the injection part of the rock is dissolved due to the strong reactivity, or the corrosion of the production equipment is very high at high temperature. Must be used (Sayed et al., 2013; Carins et al., 2016; Sidaoui et al., 2018). In order to compensate for the limitations of the existing acid treatment method, the acid mixing increases the viscosity of the acid to delay the reaction between the acid and the rock by improving the volumetric sweep efficiency between the acid and the rock, and forms an efficient wormhole. (acid divergent) techniques have been studied (Nasr-El-Din et al., 2001; Carins et al., 2016).

Among them, emulsified acid is a mixture of oil and an emulsifier in hydrochloric acid to increase the viscosity of the acid, and when injected into the reservoir, the injection pressure of the fluid can be kept low. In particular, since the oil used for the production of emulsified acid encapsulates the acid, it can delay the reaction between acid and rock, as well as prevent corrosion of production facilities (Kasza et al., 2006; Madyanova et al., 2012; Sarma et al . ., 2012). At this time, in order to carry out a successful emulsified acid treatment method, it is important to secure the stability of the emulsified acid for 24 hours at room temperature for the production and transport of the emulsified acid, and for 4 hours for the injection of the fluid in the reservoir at high temperature (70°C or higher). do (Sokhanvarian et al., 2019; Song et al., 2021).

However, most of the research on the acid treatment method for emulsified acid so far has mainly focused on the calculation of solubility and diffusion coefficient by preparing emulsified acid using a cationic emulsifier alone and performing acid-rock reaction experiments under laboratory conditions. In addition, research on the manufacture of W/O emulsifiers that secure stability at both room and high temperatures using a mixed emulsifier is insignificant. Sayed et al. (2012) prepared emulsified acids using cationic emulsifiers and derived the optimal injection rate of emulsified acids through acid treatment core flood experiments. As a result of the experiment, emulsified acid improved the permeability of the core sample by forming an efficient wormhole without face dissolution regardless of the injection rate. However, the emulsified acid prepared in this study secured stability for more than 48 hours at a room temperature of 24°C, but showed low stability, which was separated within 1.5 hours at a high temperature of 110°C. Sidaoui et al. (2018) prepared emulsified acids by concentration of emulsifiers using cationic emulsifiers, and stability evaluation was performed at high temperature (120° C.) immediately after emulsifying acid was prepared. As a result of the stability evaluation, the stability of the emulsified acid containing 1.5 wt% of the emulsifier was the best, but it started to separate into oil and acid after 2 hours, and after 4 hours, the volume of the stable emulsified acid was 70 It showed instability below vol%. Yousufi et al. (2018) confirmed that the emulsified acid forms an efficient form of wormholes through an acid treatment core flow experiment after preparing an emulsified acid using a nonionic emulsifier. However, the emulsified acid prepared in this study was stable for more than 5 hours at a high temperature of 70°C, but showed low stability for less than 9 hours at room temperature.

As a result of the analysis of the preceding studies, emulsified acid supplemented the rapid reactivity of hydrochloric acid and showed that it was more efficient than using hydrochloric acid alone, but it is judged that field application is difficult because it does not have stability at room temperature or high temperature. Therefore, it is essential to study the emulsified acid production that secures stability in both room temperature and high temperature conditions for field application.

US Patent 8053395

As a result of research efforts to develop an emulsified acid composition that can be applied to the field by solving the problems of the prior art described above, the present inventors developed an emulsified acid composition capable of securing both stability at room temperature and high temperature and a method for preparing the same, The invention was completed.

Therefore, an object of the present invention is to adjust the concentration of hydrochloric acid, acid-oil ratio, two or more emulsifiers, emulsifier mixing ratio and emulsifier concentration, etc. at room temperature required for production and transport of the emulsified acid composition. An emulsified acid composition of a new composition capable of successfully carrying out the acid treatment method of a carbonate rock reservoir by securing stability for over 24 hours of To provide a manufacturing method.

Another object of the present invention is to provide an effective acid-rock reaction delay effect in carbonate rocks with low permeability or heterogeneity when an emulsified acid composition for acid treatment of a carbonate rock reservoir, which has both stability at room temperature and high temperature, is injected into a carbonate rock reservoir. It is to provide an acid treatment method for carbonate rock reservoirs that can increase productivity by being slowly injected into carbonate rock reservoirs at oil development sites and acting for long distances.

Objects of the present invention are not limited to the objects mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above-described object of the present invention, the present invention provides an emulsified acid composition for acid treatment of carbonate rock reservoirs comprising an aqueous hydrochloric acid solution and a mixed emulsifier diesel solution in an amount of 65 to 75% by volume: 25 to 35% by volume.

In a preferred embodiment, the concentration of hydrochloric acid in the aqueous hydrochloric acid solution is 5 wt% to 20 wt%.

In a preferred embodiment, the mixed emulsifier diesel solution has a concentration of 1 wt% to 3 wt% of the mixed emulsifier.

In a preferred embodiment, the mixed emulsifier is a mixture of a cationic emulsifier and a nonionic emulsifier in a predetermined ratio.

In a preferred embodiment, the cationic emulsifier is cetyl trimethylammonium bromide (CTAB), and the nonionic emulsifier is SPAN 80 (sorbitan monooleate).

In a preferred embodiment, the predetermined ratio is a ratio at which a Hydrophile-Lipophile Balance (HLB) value determined in Equation 1 below is 5.0 to 5.5.

[Equation 1]

는 양이온성유화제의 HLB 값,

는 비이온성유화제의 HLB 값이며,

는 양이온성유화제의 무게,

는 비이온성유화제의 무게이다. here,

is the HLB value of the cationic emulsifier,

is the HLB value of the nonionic emulsifier,

is the weight of the cationic emulsifier,

is the weight of the nonionic emulsifier.

In a preferred embodiment, it further comprises a corrosion inhibitor in a concentration of 0.1 to 0.5% by weight.

In a preferred embodiment, the corrosion inhibitor is Propargyl alcohol.

In a preferred embodiment, it is stable for 24 hours or more at room temperature, and is stable for 4 hours or more at 70°C to 120°C.

In addition, the present invention comprises the steps of preparing an aqueous hydrochloric acid solution; Preparing a mixed emulsifier diesel solution; and mixing the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution in an amount of 65 to 75 vol%: 25 to 35 vol% and stirring.

In a preferred embodiment, the concentration of hydrochloric acid in the aqueous hydrochloric acid solution is 5 wt% to 20 wt%.

In a preferred embodiment, adding a corrosion inhibitor to the aqueous hydrochloric acid solution and stirring;

In a preferred embodiment, the step of preparing the mixed emulsifier diesel solution comprises: a first stirring step of adding a mixed emulsifier to diesel so that the concentration is 1% to 3% by weight and stirring at a low speed at room temperature; and a second stirring step in which the diesel in which the mixed emulsifier is dissolved in the first stirring step is stirred at high speed.

In a preferred embodiment, the mixed emulsifier is a mixture of a cationic emulsifier and a nonionic emulsifier in a predetermined ratio.

In a preferred embodiment, the cationic emulsifier is cetyl trimethylammonium bromide (CTAB), and the nonionic emulsifier is SPAN 80 (sorbitan monooleate).

In a preferred embodiment, the predetermined ratio is a ratio at which a Hydrophile-Lipophile Balance (HLB) value determined in Equation 1 below is 5.0 to 5.5.

[Equation 1]

는 양이온성유화제의 HLB 값,

는 비이온성유화제의 HLB 값이며,

는 양이온성유화제의 무게,

는 비이온성유화제의 무게이다. here,

is the HLB value of the cationic emulsifier,

is the HLB value of the nonionic emulsifier,

is the weight of the cationic emulsifier,

is the weight of the nonionic emulsifier.

In a preferred embodiment, the corrosion inhibitor is added in a concentration of 0.1 to 0.5% by weight.

In addition, the present invention provides a method for acid treatment of a rock body of a carbonate rock storage, comprising the step of injecting any one of the above-mentioned emulsified acid composition or the emulsified acid composition prepared by any one of the above-mentioned manufacturing methods into the carbonate rock storage layer. .

In a preferred embodiment, in the emulsified acid composition, the diffusion rate in the carbonate rock storage layer is 3,410 times slower than that of hydrochloric acid.

According to the emulsified acid composition of the present invention described above, the concentration of hydrochloric acid, acid-oil ratio, specification of two or more emulsifiers, emulsifier mixing ratio and emulsifier concentration, etc. are adjusted to prepare and transport the emulsified acid composition. It is possible to perform a successful acid treatment method for carbonate rock reservoirs by securing stability at room temperature for 24 hours or more and stability for 4 hours or more at high temperature (70° C. or higher) required for fluid injection in carbonate rock reservoirs.

In addition, according to the acid treatment method of the carbonate rock storage bed of the present invention, when the emulsified acid composition for acid treatment of the carbonate rock storage layer of a new composition that has secured stability at both room temperature and high temperature is injected into the carbonate rock storage layer, the permeability is low or heterogeneous Through the effective acid-rock reaction delay effect in carbonate rock, it is slowly injected into the carbonate rock reservoir at the petroleum development site and acts over a long distance, thus improving productivity.

These technical effects of the present invention are not limited only to the range mentioned above, and even if not explicitly mentioned, the effect of the invention that can be recognized by those of ordinary skill in the art from the description of the specific content for the implementation of the invention to be described later is also of course included

)과의 그래프로 나타낸 것이다.1 is a schematic diagram showing the surface arrangement of an emulsifier.
2 is a flowchart showing an embodiment of a method for preparing an emulsified acid composition according to an embodiment of the present invention.
3a and 3b are photographs showing the results of the DROP LET TEST and the separation test, respectively, as the stability test results of the emulsified acid composition prepared with CTAB.
4a and 4b are photographs showing the results of the DROP LET TEST and the separation test as the stability test results of the emulsified acid composition prepared with SPAN 80, respectively.
5 is a result of preparing an emulsified acid composition using 15 wt% hydrochloric acid according to another embodiment of the present invention and performing a droplet test, showing the shape of the droplet of the emulsified acid composition according to the HLB value and the concentration of the emulsifier. will be.
6 is a result of preparing an emulsified acid composition using 22 wt% hydrochloric acid and performing a droplet test, and shows the shape of droplets of the emulsified acid composition according to the HLB value and the concentration of the emulsifier in a photograph.
7 is a result of preparing an emulsified acid composition using 28 wt% hydrochloric acid and performing a droplet test, showing the shape of droplets of the emulsified acid composition according to the HLB value and the concentration of the emulsifier in a photograph.
8A to 8C are graphs showing the results of a phase separation experiment for deriving an optimal mixing ratio of two emulsifiers included in the emulsified acid composition of the present invention.
9a to 9c show the emulsifier concentration obtained by performing a phase separation experiment at room temperature and high temperature to derive the optimal manufacturing conditions of the emulsified acid composition according to the concentration of hydrochloric acid and the acid-oil ratio according to the derived optimal mixing ratio of the two emulsifiers. The final relative volume graph according to
10a is a graph showing the result of measuring the apparent viscosity of the emulsified acid composition of the present invention, and FIG. 10b is a graph showing the result of calculating the empirical function value of the emulsified acid composition of the present invention.
11A to 11C are photographs comparing the rock disks before and after the RDA experiment, and FIG. 11D is a graph showing the weight reduction rate (%) according to the type of acid and the rotation speed.
12a and 12b are graphs showing the limestone dissolution rate for 20 minutes, FIG. 12b is a graph showing the limestone dissolution rate for 10 minutes, and FIGS. 12c and 12d are respectively the dissolution rate of dolomite and It shows the dissolution rate of chalk rock.
13 is a graph showing the solubility calculation results in order to compare the reactivity of hydrochloric acid and emulsified acid compositions in carbonate rocks.
14 is a relational expression (

) is shown graphically.

As for the terms used in the present invention, general terms that are currently widely used are selected as possible, but in certain cases, there are also terms arbitrarily selected by the applicant. So the meaning must be understood.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having meanings consistent with the meanings in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present invention. does not

The terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present invention, terms such as “comprise” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the description of the invention is present, but one or more other It should be understood that it does not preclude the possibility of addition or presence of features or numbers, steps, operations, components, parts, or combinations thereof.

Terms such as first, second, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

In interpreting the components, it is interpreted as including an error range even if there is no separate explicit description. In particular, when the terms "about", "substantially", etc. of degree are used, they may be construed as being used in a sense at or close to the numerical value when manufacturing and material tolerances inherent in the stated meaning are presented. .

In the case of a description of a temporal relationship, for example, 'immediately' or 'directly' when a temporal precedence is described with 'after', 'following', 'after', 'before', etc. This includes cases that are not continuous unless this is used.

Hereinafter, the technical configuration of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Like reference numbers used to describe the invention throughout the specification refer to like elements.

The technical characteristics of the present invention are the concentration of hydrochloric acid, acid-oil ratio, specification of two or more emulsifiers, the mixing ratio of the emulsifier and the concentration of the emulsifier at room temperature necessary for the production and transport of the emulsified acid composition. An emulsified acid composition of a new composition capable of successfully carrying out the acid treatment method of the carbonate rock reservoir by securing stability for more than 24 hours and stability at high temperature (over 70℃) for more than 4 hours for injection of fluid in the carbonate rock reservoir and its manufacture It's about providing a way.

That is, in the present invention, in order to ensure stability at both room temperature and high temperature, a mixed emulsifier-based emulsified acid composition is prepared, and stability evaluation is performed to determine the concentration of hydrochloric acid, acid-oil ratio, emulsifier mixing ratio and By deriving the optimal ratio to the emulsifier concentration, when injected into carbonate rocks with low permeability or heterogeneity, it is possible to carry out the acid treatment method of carbonate rock reservoirs with improved productivity through an effective acid-rock reaction delay effect.

Therefore, the emulsified acid composition for acid treatment of carbonate rock reservoirs of the present invention contains an aqueous hydrochloric acid solution and a mixed emulsifier diesel solution in an amount of 65 to 75% by volume: 25 to 35% by volume.

Here, the volume ratio of the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution is a factor affecting the content of hydrochloric acid and the stability and viscosity of the emulsified acid composition. As will be described later, it is determined by deriving an appropriate ratio experimentally. That is, if the volume of the aqueous hydrochloric acid solution is less than 65% by volume and the volume of the mixed emulsifier diesel solution exceeds 35% by volume, the phase separation of the emulsified acid composition occurs rapidly and there is a problem with low stability, and the volume of the aqueous hydrochloric acid solution exceeds 75% by volume, If the volume of the mixed emulsifier diesel solution is less than 25% by volume, there is a problem in that the amount of the oil phase to cover the aqueous phase is not sufficient, so that it is impossible to homogeneously mix the composition.

In particular, the concentration of hydrochloric acid in the hydrochloric acid solution determines the production operating cost and the efficiency of wormhole generation in the field. Experimentally, 5 wt% to 20 wt% showed the best efficiency. If the concentration of hydrochloric acid is less than 5% by weight, there is a problem that the wormhole generation efficiency is lowered because it does not sufficiently react with the storage layer.

The mixed emulsifier diesel solution is a solution in which two or more emulsifiers are dissolved using diesel as a solvent, and the concentration of the mixed emulsifier is an important factor determining the viscosity and fluid stability of the emulsified acid composition. It may be 2 wt% to 3 wt%. When the concentration of the mixed emulsifier is less than 2% by weight, the stability of the emulsion over time is lowered and there is a problem that the phase separation occurs quickly. When the concentration of the mixed emulsifier exceeds 3% by weight, the viscosity of the emulsified acid composition increases, When it increases, the injection pressure increases. This is because when the fluid is injected into the reservoir, a higher pressure is applied than the crushing pressure of the stratum, which causes the rock bodies to be crushed and the construction method to fail.

A mixed emulsifier is a mixture of two or more different types of emulsifiers, and as shown in FIG. 1, two or more different types of emulsifiers are mixed so that the HLB value is between 3 and 6, making it easy to form a W/O emulsion. This is because the arrangement of the emulsifiers at the emulsion interface becomes dense and the stability over time increases. The HLB value, an important characteristic of an emulsifier, is a characteristic indicating the degree of hydrophilicity or lipophilicity of the emulsifier. The closer to 1, the more lipophilic, the closer to 20, the more hydrophilic, and it determines the emulsion type (W/O emulsion, O/W emulsion). do. The use of the emulsifier to be used is determined according to the HLB value range, and an appropriate emulsifier should be selected in consideration of the HLB value for W/O emulsion production.

In particular, the mixed emulsifier of the present invention may be a mixture of a cationic emulsifier and a nonionic emulsifier in a certain ratio, but all known materials cannot be used for the cationic emulsifier and the nonionic emulsifier, and certain characteristics must be satisfied. That is, the cationic emulsifier has a property of increasing the stability of the emulsified acid at room temperature. As an embodiment, it may be any one selected from the group consisting of ammonium series having a long alkyl (Alkyl) chain, such as CTAB (cetyl trimethylammonium bromide). have. Among cationic emulsifiers, cetyl trimethyl ammonium bromide (CTAB) forms an O/W emulsion that cannot be used in the emulsified acid acid treatment method due to its high HLB value, but has the property to increase the safety of emulsified acids at room temperature. The nonionic emulsifier has a property to ensure the stability of the emulsion at high temperatures, and in one embodiment, may be a nonionic surfactant, sorbitan monooleate (SPAN 80). That is, among nonionic emulsifiers, SPAN 80 has low emulsion stability at room temperature, but has an HLB value of 4.3, which forms a W/O emulsion suitable for the emulsification acid acid treatment method, and has the advantage of securing the stability of the emulsion at high temperatures.

The mixed emulsifier of the present invention may be one in which the cationic emulsifier and the nonionic emulsifier are mixed at a ratio such that the HLB (Hydrophile-Lipophile Balance) value determined by the following Equation 1 is 5.0 to 5.5. As such, the HLB value, which is the mixing ratio of the emulsifier, is an important factor determining the shape of the emulsion. When the HLB value is set from 3 to 6, a W/O emulsified acid composition is formed. The HLB value forming the O emulsion acid composition was 5.0 to 5.5. That is, if the HLB value is less than 5.0, the stability of the emulsion is lowered and there is a problem that the phase separation phenomenon occurs quickly. because there is

[Equation 1]

는 양이온성유화제의 HLB 값,

는 비이온성유화제의 HLB 값이며,

는 양이온성유화제의 무게,

는 비이온성유화제의 무게이다. here,

is the HLB value of the cationic emulsifier,

is the HLB value of the nonionic emulsifier,

is the weight of the cationic emulsifier,

is the weight of the nonionic emulsifier.

If necessary, the emulsified acid composition for acid treatment of carbonate rock storage layer of the present invention may further contain a corrosion inhibitor at a concentration of 0.3 to 0.5 wt %. It overcomes the limitation of using a corrosion inhibitor. In other words, the emulsified acid composition for acid treatment of carbonate rock storage of the present invention has low corrosiveness of production facilities due to the form in which diesel, which is oil phase, wraps hydrochloric acid, which is aqueous phase, when injected into carbonate rock storage, but contains a small amount of corrosion inhibitor as described above. This is because the durability of production facilities can be further improved by preventing corrosion by preventing the interaction between H+ ions and the metal surface. The preservative is not limited as long as it has good compatibility with hydrochloric acid, but in one embodiment, it may be any one selected from the group of compounds containing a propargyl group, such as propargyl alcohol.

The emulsified acid composition for acid treatment of a carbonate rock storage layer of the present invention having the above-described composition is stable at room temperature for 24 hours or more, and is stable at 70° C. to 120° C. for 4 hours or more.

Next, the method for preparing an emulsified acid composition for acid treatment of a carbonate rock storage layer of the present invention comprises the steps of preparing an aqueous hydrochloric acid solution; Preparing a mixed emulsifier diesel solution; and mixing the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution at 65 to 75 vol%: 25 to 35 vol% and stirring.

The step of preparing the aqueous hydrochloric acid solution may be performed by diluting hydrochloric acid having a purity exceeding 20 wt% with deionized water so that the concentration of hydrochloric acid is 5 wt% to 20 wt%. Hydrochloric acid is an acid that is inexpensive and has good compatibility with carbonate rocks. The concentration of hydrochloric acid determines the production and operation cost in the field and the efficiency of wormhole creation. If the concentration of acid is too high during the rock body acid treatment method, it damages the production facilities and causes additional costs due to additives such as corrosion inhibitors and increases production and operation costs. On the contrary, if the concentration of hydrochloric acid is low, Since it cannot react, the efficiency of wormhole generation is lowered, so the concentration of the hydrochloric acid solution can be determined appropriately considering this.

The step of preparing the mixed emulsifier diesel solution comprises: a first stirring step of adding the mixed emulsifier to diesel so that the concentration thereof is 1% to 3% by weight and stirring at a low speed at room temperature; and a secondary stirring step of stirring the diesel in which the mixed emulsifier is dissolved in the first stirring step at high speed. The first stirring step may be performed by stirring at 200 to 400 rpm using a magnetic stirrer at room temperature, and the second stirring step may be performed by stirring at 15000 to 20000 rpm. Since the mixed emulsifier has been described above, a detailed description thereof will be omitted.

The step of mixing and stirring the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution at 65-75 vol%: 25-35 vol% is 65-75 vol%: 25-35 vol% so that the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution have an appropriate acid-oil ratio. After mixing in volume %, it can be carried out by stirring at a high speed of 18,000 rpm or more so that each component can be mixed homogeneously. That is, when using a magnetic stirrer with a relatively low rotational speed in the preparation of the emulsified acid composition, the stability of the emulsion decreases rapidly over time, but on the other hand, a high-performance mixer having a rotational speed of 18,000 rpm (revolution per minute) or more is used. This is because it is advantageous to prepare a stable emulsified acid by stirring the emulsion for a certain period of time at a high speed.

If necessary, adding a corrosion inhibitor to the aqueous hydrochloric acid solution and stirring; may be further included. At this time, the corrosion inhibitor can be added to the hydrochloric acid aqueous solution before mixing the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution and stirred at 200 to 400 rpm, that is, the corrosion of the production equipment is completely prevented despite the diffusion barrier of the emulsified acid composition. This is because it is possible to prevent corrosion by preventing the interaction between H+ ions and the metal surface by adding 0.1 wt% to 0.5 wt% of a corrosion inhibitor, which has excellent compatibility with hydrochloric acid, when preparing an emulsified acid composition. .

Next, the rock acid treatment method of the carbonate rock storage layer of the present invention comprises the step of injecting any one of the above-mentioned emulsified acid composition or the emulsified acid composition prepared by any one of the above-mentioned manufacturing methods into the carbonate rock storage layer. Here, the emulsified acid composition has a diffusion coefficient that is at least 3,410 times lower than that of hydrochloric acid in the carbonate rock reservoir, and has a diffusion coefficient that is at most 50,600 times lower than that of hydrochloric acid. Therefore, when the emulsified acid composition of the present invention is used to perform the rock acid treatment method of the carbonate rock reservoir, it is slowly injected into the carbonate rock reservoir with low permeability or heterogeneity through the acid-rock reaction delay effect and acts for a long time up to a long distance. Therefore, it is possible to improve the permeability at the oil development site.

Example 1

According to the flowchart shown in FIG. 2, an emulsified acid composition 1 was prepared as follows.

1. Preparation of hydrochloric acid solution

A 15 wt% aqueous hydrochloric acid solution was prepared by diluting hydrochloric acid having a purity of 35 wt% with deionized water (DIW).

2. Addition of corrosion inhibitor

0.3 wt% of propargyl alcohol was added to the prepared hydrochloric acid solution and stirred at room temperature at 300 rpm for 10 minutes using a magnetic stirrer to prepare an aqueous hydrochloric acid solution with a corrosion inhibitor added thereto.

3. Preparation of mixed emulsifier diesel solution

(1) Mixed emulsifier

After preparing CTAB (Sigma-Aldrich) as a cationic emulsifier and SPAN 80 (Sigma-Aldrich) as a nonionic emulsifier, the concentration of the mixed emulsifier is 1% by weight, and the HLB value is 4.5 to 6.5. A mixed emulsifier was prepared by mixing 0.123% by weight of CTAB and 0.877% by weight of SPAN 80 having an HLB value of 5.0 according to Table 1 calculated according to the following.

HLB value CTAB (wt%) SPAN 80 (wt%) SUM (wt%) 4.5 0.035 0.965 1.0 5.0 0.123 0.877 5.5 0.210 0.790 6.0 0.300 0.700 6.5 0.386 0.614

(2) 1st stirring step

1 wt% of a mixed emulsifier (CTAB 0.123 wt% and SPAN 80 0.877 wt%) was added to the diesel solution and stirred at 300 rpm using a magnetic stirrer at room temperature to perform a first stirring step.

(2) Second stage of stirring

A mixed emulsifier diesel solution was prepared by stirring the diesel solution in which the mixed emulsifier was dissolved at a high speed of 18,000 rpm for 5 minutes using a waring mixer at room temperature.

4. Preparation of emulsified acid composition

The prepared hydrochloric acid aqueous solution and the mixed emulsifier diesel solution were mixed at 70% by volume: 30% by volume and stirred at room temperature at a high speed of 18,000 rpm for 10 minutes to form emulsified acid composition 1 (Case 1, 5.0, 70:30, 15wt%, 1wt%). ) was prepared.

Example 2

Emulsified acid composition 2 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.1845% by weight of CTAB and 1.3155% by weight of SPAN 80 with a concentration of 1.5% by weight and an HLB value of 5.0. , 5.0, 70:30, 15wt%, 1.5wt%) were prepared.

Example 3

Emulsified acid composition 3 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.246% by weight of CTAB and 1.754% by weight of SPAN 80 having an HLB value of 5.0 and a concentration of 2% by weight of the mixed emulsifier. , 5.0, 70:30, 15wt%, 2wt%) were prepared.

Example 4

Emulsified acid composition 4 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.3075% by weight of CTAB and 2.1925% by weight of SPAN 80 having an HLB value of 5.0 and a concentration of 2.5% by weight of the mixed emulsifier. , 5.0, 70:30, 15 wt%, 2.5 wt%) were prepared.

Example 5

Emulsified acid composition 5 (Case 1) in the same manner as in Example 1, except that the concentration of the mixed emulsifier was 3% by weight, and the mixed emulsifier was prepared by mixing 0.369% by weight of CTAB and 2.631% by weight of SPAN 80 having an HLB value of 5.0. , 5.0, 70:30, 15wt%, 3wt%) were prepared.

Example 6

Emulsified acid composition 6 (Case 1, 5.5, 70:30, 15 wt%, 1 wt%) were prepared.

Example 7

Emulsified acid composition 7 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.315 wt% of CTAB and 1.185 wt% of SPAN 80 having a concentration of 1.5 wt% and an HLB value of 5.5 , 5.5, 70:30, 15 wt%, 1.5 wt%) were prepared.

Example 8

Emulsified acid composition 8 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.420 wt% of CTAB and 1.580 wt% of SPAN 80 having a concentration of 2 wt% and an HLB value of 5.5 , 5.5, 70:30, 15wt%, 2wt%) were prepared.

Example 9

Emulsified acid composition 9 (Case 1) in the same manner as in Example 1, except that the mixed emulsifier was prepared by mixing 0.525 wt% of CTAB and 1.975 wt% of SPAN 80 having a concentration of 2.5 wt% and an HLB value of 5.5 , 5.5, 70:30, 15wt%, 2.5wt%) were prepared.

Example 10

Emulsified acid composition 10 (Case 1) in the same manner as in Example 1, except that the concentration of the mixed emulsifier was 3% by weight, and the mixed emulsifier was prepared by mixing 0.630% by weight of CTAB and 2.370% by weight of SPAN 80 having an HLB value of 5.5. , 5.5, 70:30, 15wt%, 3wt%) were prepared.

Comparative Examples 1 to 15

Comparative Example Compositions 1 to 15 were obtained in the same manner as in Example 1 except for having the composition shown in Table 2 below.

Comparative Examples 16 to 40

Comparative Example Compositions 16 to 40 were obtained in the same manner as in Example 1, except for having the composition shown in Table 3 below.

Set Case HLB values Mixed emulsifier concentration (wt%) note Set 1 Case 2
- Hydrochloric acid solution concentration 22wt%
- Acid-Oil volume ratio 70:30
4.5 One Comparative Example Composition 16 1.5 Comparative Example Composition 17 2 Comparative Example Composition 18 2.5 Comparative Example Composition 19 3 Comparative Example Composition 20 5 One Comparative Example Composition 21 1.5 Comparative Example Composition 22 2 Comparative Example Composition 23 2.5 Comparative Example Composition 24 3 Comparative Example Composition 25 5.5 One Comparative Example Composition 26 1.5 Comparative Example Composition 27 2 Comparative Example Composition 28 2.5 Comparative Example Composition 29 3 Comparative Example Composition 30 6 One Comparative Example Composition 31 1.5 Comparative Example Composition 32 2 Comparative Example Composition 33 2.5 Comparative Example Composition 34 3 Comparative Example Composition 35 6.5 One Comparative Example Composition 36 1.5 Comparative Example Composition 37 2 Comparative Example Composition 38 2.5 Comparative Example Composition 39 3 Comparative Example Composition 40

Comparative Examples 41 to 65

Comparative Example Compositions 41 to 65 were obtained in the same manner as in Example 1 except for having the composition shown in Table 4 below.

Set Case HLB values Mixed emulsifier concentration (wt%) note Set 1 Case 3
- Hydrochloric acid solution concentration 28wt%
- Acid-Oil volume ratio 70:30
4.5 One Comparative Example Composition 41 1.5 Comparative Example Composition 42 2 Comparative Example Composition 43 2.5 Comparative Example Composition 44 3 Comparative Example Composition 45 5 One Comparative Example Composition 46 1.5 Comparative Example Composition 47 2 Comparative Example Composition 48 2.5 Comparative Example Composition 49 3 Comparative Example Composition 50 5.5 One Comparative Example Composition 51 1.5 Comparative Example Composition 52 2 Comparative Example Composition 53 2.5 Comparative Example Composition 54 3 Comparative Example Composition 55 6 One Comparative Example Composition 56 1.5 Comparative Example Composition 57 2 Comparative Example Composition 58 2.5 Comparative Example Composition 59 3 Comparative Example Composition 60 6.5 One Comparative Example Composition 61 1.5 Comparative Example Composition 62 2 Comparative Example Composition 63 2.5 Comparative Example Composition 64 3 Comparative Example Composition 65

Comparative Examples 66 to 75

Comparative Example Compositions 66 to 75 were obtained in the same manner as in Example 1 except for having the composition shown in Table 5 below.

Set Case Acid-Oil Volume Ratio Mixed emulsifier concentration (wt%) note Set 2 Case 4
- Hydrochloric acid solution concentration 15wt%
-HLB values 5
50:50 One Comparative Example Composition 66 1.5 Comparative Example Composition 67 2 Comparative Example Composition 68 2.5 Comparative Example Composition 69 3 Comparative Example Composition 70 60:40 One Comparative Example Composition 71 1.5 Comparative Example Composition 72 2 Comparative Example Composition 73 2.5 Comparative Example Composition 74 3 Comparative Example Composition 75 70:30 One Emulsified acid composition 1 1.5 Emulsified acid composition 2 2 Emulsified acid composition 3 2.5 Emulsified acid composition 4 3 Emulsified acid composition 5

Comparative Examples 76 to 90

Comparative Example Compositions 76 to 85 were obtained in the same manner as in Example 1 except for having the composition shown in Table 6 below.

Set Case Acid-Oil Volume Ratio Mixed emulsifier concentration (wt%) note Set 2 Case 5
- Hydrochloric acid solution concentration 22wt%
-HLB values 5
50:50 One Comparative Example Composition 76 1.5 Comparative Example Composition 77 2 Comparative Example Composition 78 2.5 Comparative Example Composition 79 3 Comparative Example Composition 80 60:40 One Comparative Example Composition 81 1.5 Comparative Example Composition 82 2 Comparative Example Composition 83 2.5 Comparative Example Composition 84 3 Comparative Example Composition 85 70:30 One Comparative Example Composition 21 1.5 Comparative Example Composition 22 2 Comparative Example Composition 23 2.5 Comparative Example Composition 24 3 Comparative Example Composition 25

Comparative Examples 91 to 105

Comparative Example Compositions 86 to 100 were obtained in the same manner as in Example 1, except for having the composition shown in Table 7 below.

Set Case Acid-Oil Volume Ratio Mixed emulsifier concentration (wt%) note Set 2 Case 6
- Hydrochloric acid solution concentration 28wt%
-HLB values 5
50:50 One Comparative Example Composition 86 1.5 Comparative Example Composition 87 2 Comparative Example Composition 88 2.5 Comparative Example Composition 89 3 Comparative Example Composition 90 60:40 One Comparative Example Composition 91 1.5 Comparative Example Composition 92 2 Comparative Example Composition 93 2.5 Comparative Example Composition 94 3 Comparative Example Composition 95 70:30 One Comparative Example Composition 46 1.5 Comparative Example Composition 47 2 Comparative Example Composition 48 2.5 Comparative Example Composition 49 3 Comparative Example Composition 50

Experimental method

1. Droplet test

In order to confirm the form of the prepared emulsified acid composition, the droplet test can be performed as follows. After filling a 100 ml beaker with deionized water, the prepared emulsified acid composition is dropped into deionized water using a pipette. When a droplet of the emulsified acid composition is dropped into water, it is determined that the W/O emulsified acid composition is formed if the droplet shape is maintained without being separated from the water. Conversely, when droplets of the emulsified acid composition do not maintain their shape and are dispersed in water, the water-soluble acid forms a continuous phase, which is not suitable for the emulsified acid treatment method.

2. Phase separation test

The emulsified acid composition, in which the form of a W/O emulsion suitable for the emulsified acid acid treatment method was confirmed through the droplet test, is subjected to a phase separation test at room temperature (25°C) and high temperature (90°C). In order to prevent separation of acid and oil in field application, it is very important to understand the stability of the emulsified acid composition with respect to temperature and time, so measure the relative volume according to temperature and time and determine the stability of the emulsified acid composition. . The relative volume represents the ratio of the volume of the emulsified acid (phase volume) maintaining stability with respect to the total volume of the entire fluid, and can be expressed as Equation 2 below.

[Equation 2]

The phase separation test is carried out in an oven that can keep the temperature constant by putting the prepared emulsified acid in a measuring cylinder. Put the prepared emulsified acid in a 50 ml measuring cylinder and place it in a low temperature oven. Measure the relative volume at 1 hour intervals while confirming the stability for 24 hours at room temperature. After 24 hours, the phase separation test at high temperature is carried out only for emulsified acids whose relative volume is 95 vol% or more and stability at room temperature is secured. The emulsified acid is placed in a high temperature oven and stability is checked for 4 hours. At this time, measure the relative volume of emulsified acid every 30 minutes. When the relative volume is maintained at 95 vol% or more even after 4 hours at high temperature (70°C or higher), it is finally judged to be a stable emulsified acid, and the relative volume measured at room temperature and high temperature is shown as a graph over time.

In order to perform the phase separation test at room temperature, JEIO TECH's low-temperature oven L-11 was used. IL-11 can set the temperature from 0℃ up to 60℃, and has the advantage of maintaining constant conditions by carefully maintaining the temperature with an error of 0.1℃. In addition, in order to proceed with the phase separation test at high temperature, a high-temperature oven MOV-212F manufactured by Sanyo was used. MOV-212F can control the temperature from the lowest temperature of 40℃ to the highest 200℃, and it has the advantage of being able to set the set temperature within a short time and keep it constant.

Experimental Example 1

In order to compare the performance of the emulsified acid composition prepared using the mixed emulsifier according to the present invention, an emulsified acid was prepared using the cationic emulsifier CTAB alone and the performance was evaluated, and the results are shown in FIGS. 3a and 3b.

The cationic emulsifier CTAB having a hydrophilic HLB value of 10 did not maintain the shape of droplets in water as shown in FIG. 3a as a result of a droplet test immediately after preparing the emulsified acid, but formed an O/W emulsion that was dissolved in water. This is because the continuous phase of the emulsion is formed of water-soluble hydrochloric acid, and when it is used, the hydrochloric acid and the dark body or production equipment come into direct contact, which is not suitable for the emulsified acid treatment method. After performing the droplet test, a phase separation test was performed. As a result of the phase separation test at room temperature, as shown in FIG. 3b, phase separation of the emulsion did not occur for 24 hours or more, and stability was maintained. However, as a result of the phase separation test at high temperature, it was confirmed that all phases were separated within 1 hour. Therefore, it was confirmed that CTAB having hydrophilic properties forms an O/W emulsion and has low stability at high temperature, but enhances the stability of the emulsion at room temperature.

Experimental Example 2

In order to compare the performance of the emulsified acid composition prepared using the mixed emulsifier according to the present invention, an emulsified acid was prepared using the nonionic emulsifier SPAN 80 alone and the performance was evaluated, and the results are shown in FIGS. 4a and 4b.

As a result of preparing the emulsified acid using the nonionic emulsifier SPAN 80 alone, it was confirmed that the emulsified acid droplets were not dispersed in water and the shape was maintained in the droplet test as shown in FIG. 4a, which is W suitable for the emulsified acid treatment method It was determined that an /O emulsion was formed. As a result of the phase separation test after the droplet test, as shown in FIG. 4b , the oil phase and the aqueous phase were separated within 8 hours at room temperature, showing instability, but at high temperature, phase separation did not occur for more than 4 hours and the emulsion maintained a stable form. Therefore, it was determined that the nonionic emulsifier SPAN 80 has low stability at room temperature, but it is easy to form a W/O emulsion suitable for the emulsifying acid acid treatment method, and enhances the stability of the emulsion at high temperature.

Experimental Example 3

75 kinds of emulsified acid production experiments according to the concentration of hydrochloric acid, the concentration of the emulsifier, and the mixing ratio of the emulsifier in Set 1 set in Tables 2 to 4 to determine the optimal mixing ratio of CTAB and SPAN 80 according to Examples and Comparative Examples (Emulsified acid compositions 1 to 10 and Comparative Example compositions 1 to 65) were carried out and stability evaluation was performed, and the results are shown in FIGS. 5 to 7 . Cases 1 to 3 of Set 1 are each classified by the concentration of hydrochloric acid, and the droplet test results are shown in the form of a table according to the concentration of the mixed emulsifier and the HLB value.

5 is a result of Case 1 in which an emulsified acid composition was prepared using 15 wt% hydrochloric acid and a droplet test was performed, and the shape of the emulsified acid droplet according to the HLB value and the concentration of the emulsifier is shown in a photograph. As a result of the droplet test, the emulsified acid composition using 15% hydrochloric acid forms a W/O emulsion suitable for the emulsification acid treatment method when the HLB value is between 4.5 and 6.5 regardless of the concentration of the mixed emulsifier. It was confirmed that the enemy became stronger. In addition, it was confirmed that the lower the concentration of the mixed emulsifier, the thinner the droplets were formed, and the higher the concentration of the mixed emulsifier, the harder the droplets were. From these experimental results, it can be deduced that in order to prepare a W/O emulsion using 15 wt% hydrochloric acid, the HLB value of the mixed emulsifier should be between 4.5 and 6.5.

6 is a result of preparing an emulsified acid composition using 22 wt% hydrochloric acid and performing a droplet test. As a result of the test, the emulsified acid composition using 22% hydrochloric acid differs from the emulsified acid composition using 15 wt% hydrochloric acid when the HLB value is between 4.5 and 6 regardless of the concentration of the mixed emulsifier. was formed, and it was confirmed that the lower the HLB value, the harder the droplets were formed. In addition, it was confirmed that the lower the concentration of the mixed emulsifier, the thinner the emulsified acid droplet was formed, and the higher the concentration of the mixed emulsifier, the harder the emulsified acid composition droplet was formed. From these experimental results, it can be seen that even when 22 wt% hydrochloric acid is used, the HLB value of the mixed emulsifier must be between 4.5 and 6 to prepare a W/O emulsion.

7 is a result of preparing an emulsified acid composition using 28 wt% hydrochloric acid and performing a droplet test. As a result of the test, the emulsified acid composition using 28 wt% hydrochloric acid was suitable for the emulsified acid treatment method when the HLB value was between 4.5 and 6, regardless of the concentration of the mixed emulsifier, just like the emulsified acid composition using 22 wt% hydrochloric acid. An emulsion was formed. Also, as in the previous experiments, it was confirmed that the lower the HLB value and the higher the concentration of the mixed emulsifier, the harder the droplets were formed. However, when the mixed emulsifier of the same concentration was used, it was confirmed that the droplet was relatively dilute compared to the emulsified acid composition prepared using 22 wt% hydrochloric acid. From these experimental results, it was found that even when 28 wt% hydrochloric acid was used, the HLB value of the mixed emulsifier should be between 4.5 and 6 to prepare a W/O emulsion.

Experimental Example 4

As a result of the droplet test, a phase separation test was conducted on the emulsified acid composition that formed the W/O emulsion. After performing the phase separation test at room temperature, only the stable emulsified acid composition whose relative volume was maintained at 95 vol% or higher was subjected to a phase separation test at high temperature. and the test results are graphically shown in FIGS. 8a to 8c and 9a to 9c, respectively, and the final relative volume according to the concentration of the mixed emulsifier is shown. In the graph, the x-axis represents the concentration of the emulsifier and the y-axis represents the relative volume of the emulsified acid. A stable emulsified acid should have a relative volume of 95 vol% or more, and the relative volume 95 vol% standard is indicated by a solid black line and a hatched area in the graph. That is, it is an emulsified acid composition that secures stability when the graph is located at the top of the black solid line, and is judged to be an unstable emulsified acid composition due to phase separation when located below the black solid line.

First, the results of the phase separation experiment of Set 1 for deriving the optimal mixing ratio of the mixed emulsifier are shown in FIGS. 8A to 8C . As a result of the analysis, it was confirmed that the HLB value of the mixed emulsifier should be set to be between 4.5 and 6 regardless of the concentration of hydrochloric acid in order to prepare a W/O emulsion suitable for the emulsified acid treatment method in all cases. It was confirmed that the higher the concentration, the narrower the range. In addition, in Case 1 using 15 wt% hydrochloric acid, many emulsified acid compositions were prepared that secured stability at both room temperature and high temperature. It was impossible to prepare an emulsified acid composition with stability. In particular, in Case 3, where the concentration of hydrochloric acid was highest, the stability of the emulsified acid composition was found to be even lower. This is a phenomenon that occurs when the concentration of an acid of 15 wt% or more is higher than the diffusion barrier limit of the emulsion and the bonding structure of the emulsifier collapses.

As a result of the experiment, in case 1 to case 3 of Set 1, when the HLB value of the mixed emulsifier was set to 5, the stability of the emulsion with time was maintained the highest, and the optimal mixing ratio of the mixed emulsifier was set to 5 and the HLB value was set to 5. Compositions of case 4 to case 6 of Set 2 were set as shown in Tables 5 to 7.

That is, after deriving the optimal mixing ratio of the mixed emulsifier in Set 1, 45 experiments of Set 2 set in Tables 5 to 7 to derive the optimal manufacturing conditions of the emulsified acid composition according to the concentration of hydrochloric acid and the acid-oil ratio was performed. In the experiment of Set 2, the W/O emulsion was confirmed when the droplet test was performed in all cases, so the results were not presented individually. Relative volumes are indicated and presented graphically.

From these experimental results, it was confirmed that the lower the added amount of the mixed emulsifier or the higher the oil ratio, the lower the stability over time, and the higher the phase separation phenomenon, the unstable emulsion was formed. In particular, the higher the concentration of hydrochloric acid at the same acid-oil ratio, the more phase separation occurred, which was confirmed to be the same as the result of Set 1 above. In particular, it was impossible to prepare a W/O emulsion that secured stability when 22 wt% and 28 wt% of high-concentration hydrochloric acid were used regardless of the acid-oil ratio. As a result, when the acid-oil ratio is set to 65-75 vol%: 25-35 vol% and 5 to 20 wt% hydrochloric acid is used, phase separation does not occur at room temperature and high temperature when 1 to 3 wt% or more of the mixed emulsifier is added. It was confirmed that a W/O emulsion maintaining stability was formed.

Experimental Example 5

The fluid properties of the emulsified acid composition 3 prepared in Example 3 were analyzed as follows, and the results are shown in FIGS. 10a and 10b.

는 62.132, 무차원 멱함수 지수

은 -0.385로 산출되었다. 그래프의

값은 0.9541로, 측정한 점성도 값이 유효한 것으로 판단하였다.First, the viscosity, which is a basic rheological property of emulsified acids, was measured. Anton Paar's Lovis Viscometer 2000M micro viscometer was used, and the apparent viscosity according to the shear rate was measured and graphically shown as shown in FIG. 10A. As a result of viscosity measurement, emulsified acid, which is a non-Newtonian fluid, showed a shear reduction phenomenon that the viscosity decreased as the shear rate increased, and the power law consistency index at this time.

is 62.132, a dimensionless power exponent

was calculated as -0.385. of the graph

The value was 0.9541, and it was determined that the measured viscosity value was valid.

을 계산하였다. 함수식은 도 10b에 도시된 바와 같이

로 산출되었으며,

값은 0.9899로 우 높은 것으로 확인되었다. 앞서 점성도를 측정하여 산출한 무차원 멱함수 지수

값 -0.385을 함수식에 대입하여 함수 값 0.644를 얻었다. 산출한 점성 계수 및 경험적 함수 값은 유화산의 유효확산계수를 산출하기 위한 중요한 인자로 활용하였다.Next, based on the empirical function formula derived through experiments by de-Roziers et al . (1994), it is an essential factor in deriving the diffusion coefficient.

was calculated. The function formula is as shown in Fig. 10b

was calculated as

The value was 0.9899, which was confirmed to be very high. The dimensionless power function index calculated by measuring the viscosity previously

By substituting the value -0.385 into the function expression, a function value of 0.644 was obtained. The calculated viscosity coefficient and empirical function value were used as important factors for calculating the effective diffusion coefficient of emulsified acid.

Experimental Example 6

After comparing the rock disks before and after the RDA experiment, the results are shown in FIGS. 11A to 11C.

It can be seen that the dissolution of the rocks was more when hydrochloric acid was used than when the emulsified acid composition 3 was used for all three cancer types. you can see In particular, considering that the LH and CH experiments were performed at room temperature, the emulsified acid composition of the present invention is judged to be effective in delaying the reaction between acid and rock at high temperature.

This is shown as in Fig. 11d, which is a weight loss graph. In the case of the experiment using the emulsified acid composition of the present invention, at the same disk rotation speed, limestone showed a weight loss about 2.4 times higher than that of dolomite or chalkstone, and through this, the emulsified acid composition was in the order of chalkite-dolomite-limestone at high temperature. It is considered to be advantageous in delaying the reaction between acid and dark body.

Experimental Example 7

Since it is difficult to analyze the results of the acid and carbonate rock reaction experiments only with photographs, ICP-OES component analysis was performed to express the results of the acid-rock reaction experiment in quantitative terms. Calcium and magnesium ions, which are the main components of carbonate minerals, were measured by filtering the samples collected through the experiment for component analysis, and then diluting them 100 times, 1,000 times, and 10,000 times, and the ICP-OES component analysis results are shown in FIGS. It is also shown as a graph of ion concentration over time.

Prior to analysis, a criterion for calculating the slope of the graph for calculating solubility was determined. As shown in FIG. 12A , when all of the slopes for 20 minutes during the experiment are used, an accurate result cannot be calculated because the deviation between each point is large. Therefore, in the present invention, the slope was calculated using the slope of the graph for the initial 10 minutes as shown in FIG. 12b based on previous studies, and solubility and diffusion coefficient were derived (Sayed et al ., 2012, Sayed et al ., 2018, Yoo et al.) al ., 2018).

As a result of the analysis, it was confirmed that the dissolution of the core sample was continuously made as time passed, as the ion concentration increased with time in all experiments. Through this, it was judged that the reaction between acid and rock was carried out in a state of limited mass movement in all experiments, and the RDA experiment was successful. In addition, it can be seen that the solubility of the emulsified acid composition increases as the disk rotation speed increases for all limestone, dolomite, and chalkite samples, and it is judged that the disk rotation speed is a factor affecting the reaction of emulsified acid.

500 rpm was selected to compare the reactivity of hydrochloric acid and emulsified acid compositions at the same disk rotation speed. In the case of limestone, it can be seen that the solubility of LH using hydrochloric acid at room temperature and L5 using an emulsified acid composition at high temperature are similar. In the case of dolomite, all cases were tested at high temperature, and at this time, DH shows a steep slope more than twice that of D5. In the case of chalk rock, although the CH experiment was performed at room temperature, the slope was calculated to be higher than that of C5, where the experiment was performed at a high temperature. Through this, it is judged that the emulsified acid composition is advantageous in delaying the rapid reactivity of hydrochloric acid.

Experimental Example 8

RDA was performed to analyze acid-rock reactivity, and solubility and diffusion coefficients can be derived using the results. The change in the ion concentration with time calculated through the RDA experiment is graphed as shown in FIGS. 12A to 12D, and then the slope is calculated, and the solubility is derived by dividing the slope by the reaction area of the carbonate rock core sample. In this case, the reaction area of the core sample reacting with the acid may be expressed as the surface area of the underside of the sample, and the surface area is as shown in Equation (3).

[Equation 3]

, 여기서

이다.

, here

to be.

The diameters of the rock disks used in this experiment were all the same, and the surface area of the rock disks was derived by applying the measured porosity to each. Next, solubility was calculated using the slope of the graph and the surface area of the disk, and the results are shown in Table 8. The solubility of hydrochloric acid case was calculated as limestone 2.83E-04 gmol/cm ² s, dolomite 2.85E-04 gmol/cm ² s, and chalkite 1.60E-04 gmol/cm ² os, and in the case of emulsified acid, limestone Silver 3.61E-05 ~ 9.26E-04 gmol/cm ² s, Dolomite 7.94E-05 ~ 2.12E-04 gmol/cm ² s, Cretaceous 6.03E-06 ~ 1.66E-04 gmol/cm ² ㅇ A value between s was derived.

Dissolution rate Limestone Dolomite Chalk Acid type RPM HCl 500 2.83E-04 2.85E-04 1.60E-04 Emulsified acid composition 3 [EA] 100 3.61E-05 7.94E-05 6.03E-06 300 1.59E-04 9.68E-05 1.89E-05 500 3.99E-04 1.27E-04 4.10E-05 750 6.77E-04 1.76E-04 9.05E-05 1,000 9.26E-04 2.12E-04 1.66E-04

In addition, in order to compare the reactivity of hydrochloric acid and emulsified acid composition 3 (EA) in carbonate rocks, solubility calculation results are shown in FIG. 13 . In the case of limestone, the solubility of L5 using emulsified acid composition 3 was calculated to be about 1.4 times higher than that of LH using hydrochloric acid. In the case of dolomite, all cases were tested at high temperature, and it is shown that DH has more than twice the solubility than D5. Through this, it is determined that the emulsified acid composition of the present invention can slow the rapid reaction with acid in dolomite. In the case of chalk, the reaction with hydrochloric acid at room temperature was explosive, but it can be seen that the reactivity with the emulsified acid composition at high temperature is very low. In particular, in the case of chalkstone, the experimental results were expected to be similar to those of limestone, but the opposite result was found. It is determined that the content of impurities such as SiO ₂ in the core sample has an important effect on the acid-rock reaction.

Experimental Example 9

Before deriving the diffusion coefficient, the variable values for calculating the F function value are summarized in Table 9.

Index note values

the mass transfer rate of H ⁺ from the bulk to the disk dissolution rate

Empirical function 0.644

the concentration of H ⁺ 0.15

Power-law consistency index 62.132

Dimensionless power-law index 0.615

the fluid density 1.006

disk radius 1.9

the disk rotational speed 100, 300, 500, 750, 1,000

는 RDA 실험을 통해 산출한 각 case의 용해도이며 표 8과 같다.

는 실험에 사용된 산 용액의 농도를 나타내며,

와

,

,

는 유화산 유체의 특성,

와

는 코어 디스크의 반지름 및 디스크의 회전속도이다.

is the solubility of each case calculated through the RDA experiment and is shown in Table 8.

represents the concentration of the acid solution used in the experiment,

Wow

,

,

is the characteristic of emulsified fluid,

Wow

is the radius of the core disk and the rotational speed of the disk.

Table 9 was substituted into Equation 4 to calculate the F function value, and is shown in Table 10.

[Equation 4]

= 경험적 함수(empirical function),

= 유체 밀도(g/cm³),

= 멱함수 법칙 일관성 지수(g/cmㅇs^2-n),

= 무차원 멱함수 지수,

= 디스크 회전속도(rad/s),

= 확산계수(cm²/s) 이다.here,

= empirical function,

= fluid density (g/cm ³ ),

= power law consistency index (g/cmㅇs ^2-n ),

= dimensionless power exponent,

= disk rotation speed (rad/s),

= diffusion coefficient (cm ² /s).

F function Limestone Dolomite Chalk RPM

Emulsified
Acid 15.53 5.29E-06 1.16E-05 8.84E-07 29.88 2.33E-05 1.42E-05 2.77E-06 40.50 5.85E-05 1.86E-05 6.01E-06 51.57 9.93E-05 2.58E-05 1.33E-05 61.20 1.36E-04 3.11E-05 2.43E-05

)과의 그래프로 도시하였다. 마지막으로, 그래프의 기울기를 활용하여 표 11과 같이 유화산의 유효확산계수를 산출하였다. 이때, 염산의 확산계수는 Yoo(2017)와 Park(2018)이 활용한 뉴턴 유체의 확산계수 산출 법을 활용하였다. The calculated F function value is expressed in the relational expression (

) and is shown as a graph. Finally, using the slope of the graph, the effective diffusion coefficient of emulsified acid was calculated as shown in Table 11. In this case, for the diffusion coefficient of hydrochloric acid, the Newtonian fluid diffusion coefficient calculation method used by Yoo (2017) and Park (2018) was used.

Core Slope

(cm²/s)HCl

(cm ² /s) Emulsified Acid

(cm ² /s)

(times) Limestone 3.00E-05 5.60E-04 1.64E-07 3.41E+03 Dolomite 5.00E-06 5.66E-04 1.12E-08 5.06E+04 Chalk 6.00E-06 2.38E-04 1.47E-08 1.62E+04

As a result of the diffusion coefficient calculation, the emulsified acid composition was 3,410 times to 50,600 times lower than that of hydrochloric acid, despite the fact that hydrochloric acid experiments were performed on limestone and chalkite at room temperature. Through this, it is judged that the emulsified acid composition is effective in delaying the fast and strong reactivity of hydrochloric acid and carbonate rocks with low permeability or heterogeneity at high temperatures. is expected to appear larger.

Although the present invention has been illustrated and described with reference to preferred embodiments as described above, it is not limited to the above-described embodiments, and those of ordinary skill in the art to which the present invention pertains within the scope not departing from the spirit of the present invention Various changes and modifications will be possible.

Claims (19)

Hydrochloric acid aqueous solution and mixed emulsifier diesel solution are included in 65-75 vol%: 25-35 vol%,
The mixed emulsifier diesel solution has a concentration of 1 wt% to 3 wt% of the mixed emulsifier,
The mixed emulsifier is an emulsified acid composition for acid treatment of a carbonate rock storage layer, characterized in that a cationic emulsifier and a nonionic emulsifier are mixed in a predetermined ratio.
The method of claim 1,
The hydrochloric acid aqueous solution is an emulsified acid composition for acid treatment of carbonate rock storage, characterized in that the concentration of hydrochloric acid is 5% to 20% by weight.
delete delete The method of claim 1,
The cationic emulsifier is cetyl trimethylammonium bromide (CTAB), and the nonionic emulsifier is SPAN 80 (sorbitan monooleate).
The method of claim 1,
The predetermined ratio is an emulsified acid composition for acid treatment of carbonate rock storage, characterized in that the ratio is 5.0 to 5.5 HLB (Hydrophile-Lipophile Balance) value determined by the following formula (1).
[Equation 1]

here,

is the HLB value of the cationic emulsifier,

is the HLB value of the nonionic emulsifier,

is the weight of the cationic emulsifier,

is the weight of the nonionic emulsifier.
The method of claim 1,
Emulsified acid composition for acid treatment of carbonate rock storage layer, characterized in that it further comprises a corrosion inhibitor in a concentration of 0.1 to 0.5% by weight.
8. The method of claim 7,
The emulsified acid composition for acid treatment of carbonate rock storage layer, characterized in that the corrosion inhibitor is Propargyl alcohol.
9. The method of any one of claims 1, 2, 5 to 8,
An emulsified acid composition for acid treatment of carbonate rock storage, characterized in that it has stability not to be separated into oil and acid at room temperature for more than 24 hours, and stability not to be separated into oil and acid at 70°C to 120°C for more than 4 hours.
preparing an aqueous hydrochloric acid solution; Preparing a mixed emulsifier diesel solution; and mixing the hydrochloric acid aqueous solution and the mixed emulsifier diesel solution at 65 to 75 vol%: 25 to 35 vol% and stirring.
The step of preparing the mixed emulsifier diesel solution comprises: a first stirring step of adding a mixed emulsifier to diesel so that the concentration thereof is 1% to 3% by weight and stirring at a low speed at room temperature; and a second stirring step of stirring the diesel in which the mixed emulsifier is dissolved in the first stirring step at high speed;
The mixed emulsifier is a method for producing an emulsified acid composition for acid treatment of a carbonate rock storage layer, characterized in that a cationic emulsifier and a nonionic emulsifier are mixed in a predetermined ratio.
11. The method of claim 10,
The hydrochloric acid aqueous solution is a method for producing an emulsified acid composition for acid treatment of carbonate rock storage, characterized in that the concentration of hydrochloric acid is 5% to 20% by weight.
11. The method of claim 10,
The method for producing an emulsified acid composition for acid treatment of carbonate rock storage layer further comprising; adding a corrosion inhibitor to the aqueous hydrochloric acid solution and stirring.
delete delete 11. The method of claim 10,
The cationic emulsifier is cetyl trimethylammonium bromide (CTAB), and the nonionic emulsifier is SPAN 80 (sorbitan monooleate).
11. The method of claim 10,
The predetermined ratio is a method for producing an emulsified acid composition for acid treatment of carbonate rock storage, characterized in that the ratio is 5.0 to 5.5 in the HLB (Hydrophile-Lipophile Balance) value determined in Equation 1 below.
[Equation 1]

here,

is the HLB value of the cationic emulsifier,

is the HLB value of the nonionic emulsifier,

is the weight of the cationic emulsifier,

is the weight of the nonionic emulsifier.
13. The method of claim 12,
The method for producing an emulsified acid composition for acid treatment of carbonate rock storage layer, characterized in that the corrosion inhibitor is added at a concentration of 0.1 to 0.5% by weight.
The emulsified acid composition of any one of claims 1, 2, 5 to 8 or the emulsified acid composition prepared by the method of any one of claims 10 to 12, 15 to 17. A rock acid treatment method of a carbonate rock reservoir comprising; injecting into the carbonate rock reservoir.
19. The method of claim 18,
The emulsified acid composition is a rock body acid treatment method of a carbonate rock reservoir, characterized in that the diffusion rate is 3,410 times slower than that of hydrochloric acid in the carbonate rock reservoir.

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